In rotary internal combustion engines of the type such as exemplified in the aforesaid U.S. Patent to Wankel, various ignition devices and arrangements have been employed to ignite the fuel and air mixture within the working chambers of the engine. In these various devices the igniting device, such as a spark plug having a central electrode disposed in an insulator with one end portion projecting therefrom and forming one part of a spark-gap, is supported in the housing so that the end of the spark plug lies in close spaced relationship to the inner peripheral surface of the housing. To minimize gas leakage from the working chamber within which the fuel-air mixture is being compressed past the apex seals of the rotor, through the spark plug opening and into the next working chamber under lower pressure, the spark plug opening in the inner peripheral wall surface is closed and an ignition opening or channel is provided in the closure. As exemplified in the U.S. Patents, Weed, No. 2,020,089; Lamm, No. 3,719,174; Berkowitz, No. 3,722,480; Belzner, No. 3,512,907; and Shibagaki, No. 3,597,648, the ignition channel is of relatively small size, as compared with the size of the ante-chamber, and communicates the latter with the working chambers. In these ignition devices it has been found that auto-ignition occurs by reason of incandescence of deposits in the spark plug region. The extent of such deposits are dependent on two factors, namely, ash content of the oil employed for lubrication and the temperature of the residue carrier or surface, such as the spark plug and surfaces of the ignition channel and ante-chamber. The obvious solution to this problem is to employ ash-free oils and/or lower the operating temperature of the spark plug.
It has been proposed to effect a lower spark plug temperature, as shown in the U.S. Patent to Lamm, No. 3,719,174; and an East German Patent No. 37,392, by providing two inclined ignition channels which serve to scavenge the ante-chamber with fresh fuel and air mixture and thus produce cooler spark plug temperatures. These ignition devices have not achieved an appreciable reduction in incandescence because of encrustation on the surfaces of the two ignition channels which is attributable to their relatively long length and inclination. Also the two ignition channels for achieving turbulence in the ante-chamber did not produce any noteworthy lowering of the spark plug temperature.
Another proposal for the solution to this problem is disclosed in the U.S. Patent to Braun et al, No. 3,738,331. This ignition device, having spark plugs extending through two housing elements and involving complex and expensive machining operations to fabricate, again shows an inclined ignition channel of relatively long length although it does disclose prevention of direct hot gas impingement and heat radiation on the insulator supporting the center electrode.
It is therefore an object of this invention to provide an improved ignition device for a rotary internal combustion engine which effectively lowers the operating temperature of the firing means and adjacent surfaces and thereby achieves a reduction in deposits and possibility of auto ignition.